1. Field of the Invention
The object of the present invention is a “variable linear geometry” machine for continuously forming square tubes (i.e. square or rectangular profiles), comprising a plurality of forming stations for progressively bending a sheet strip, followed by at least one finishing station for further approaching, for the final welding, the edges of the sheet strip bent by the forming stations and by at least one final welding station of the square tube.
2. Description of the Related Art
Machines for forming square tubes by continuously bending sheet strips are well known in the art and include, in sequence, a plurality of stations in which the sheet strip is progressively deformed by pairs of conjugate rolls, i.e. having grooves presenting complementary profiles.
Such known machines present a disadvantage in that they necessitate the replacement of the pairs of rolls when one desires (or needs) to change the dimension of the tube to be produced, which leads to variable machinery downtime delays reducing system productivity.
To overcome the aforesaid serious drawback, machines for forming square tubes by continuously bending sheet are suggested in which the upper rolls of the pairs of rolls of the forming stations perform a movement along an oblique axis, placed along the bisecting line of the groove of the corresponding lower roll, which allows the same pairs of rolls to be used for producing square tubes whose dimensions fall within a more or less wide range.
In some of the known machines for forming square tubes, each station includes just one pair of rolls, bending only one edge (alternatively, the right and the left one) of the sheet strip: such machines are bulky and expensive since they must include a high number of forming stations.